I truly sympathize. My daughter had a visible rash, and after visiting 3 different doctors, and given 3 different diagnoses(fungal infection, yeast infecion, and strep) with 3 different prescriptions, I resolved to solve the problem myself.
If you wish to try there are a few things that helped use. We used 3 key items to help resolve the problem. 1) Pau D'arco tablets, 4-8 tablets a day for about a month. 2) Extra virgin coconut oil, rubbed onto the rashes after shower, and before bed(with or without a shower). 3) Tea tree oil, rubbed on after the EVCO, a couple of drops was sufficient.
I can not say that this will be the answer for you, but I can say that it worked for us, and that all of these items have a good spectrum of anti-microbial activity.
Also, I would definitely not walk into any medical facility with any body scrapings as evidence of your condition. For one thing, any samples they can use would have to be attained under clinical conditions, and for another, they would doubt you by presentation alone. Unfortunately, medical tests have to be done for a known microbe. In other words, if you have strep and you are tested for yeast, they would just get a negative result for yeast, not necessarily a notation of the presence of strep. So, if you have an atypical microbe that is infecting your skin, and they don't test for that specific microbe, the culture they use may not be adequate to culture your particular microbe, and could even kill it, so they would not even be aware of it.
Medical
Science is very limited in its diagnostic abilities, a lot moreso than the general population realizes. They make a guess, then test the guess. If it is a hit, they prescribe a medicine. If it is a miss, and they can see the rash, they make another guess and test for that. If that is a miss, they either consult another doctor/prescribe a broad spectrum
Antibiotic or antifungal/or consider it some form of contact reaction and prescribe a hydrocortisone cream. By then, if the patient is still reacting, usually the patient has wisened up to the ignorance of the doctor, and has begun to seek help elsewhere. Of course, the doctor then believes that the problem is cured, and proceeds to do the same thing with the next 'mystery' rash that comes along. And so the perpetual ignorance and misery continues.
Anyway, I hope this helps in some way.
Good luck.